Corrugated sheathing and process of forming same



Jan. 30, 1934. J. w. LEDEBOER 1,944,895 a U", nl .Il

Patented Jan. 3o, 1934 PATENT 'OFFICE CORRUGATED sliEATHING AND PROCESSoF FoaMlNG SAME John W. Ledeboer, Ambler, Pa.,

assignor to Ambler Asbestos Shingle & sheathing Company, a corporationof Pennsylvania 5 Claims.

This invention relates to corrugated sheathing and particularly to suchsheathing in composition form comprising, for instance, cement andfibrous material such as asbestos.

The object of the invention is to provide such sheathing in light strongform with relatively deep corrugations.

Further objects of the invention, particularly in the method of theformation of the sheathing will appear from the followingspecificationtaken in connection with the accompanying ldrawing in which Fig. 1 is aperspective view of the sheet as originally formed.

Fig. 2 is a diagrammatic sectional view of a portion of the corrugatingdies to form the sheet into final shape, and

Fig. 3 is a sectional view of a portion of the final corrugatedsheathing.

In the process of this invention the sheet 10 is first formed flat andof substantially uniform thickness and with its surfaces plane, thesheet being of extra width a in a direction across the corrugations.Preferably the sheet will be made by the Hatschek process, accumulatinga series of relatively thin layers as parallel laminations, or by anyother process disposing or matting the fibres llinthe general directionof the plane of the sheet as indicated, and with a compositionsufficiently diffuse to permit compacting by pressure at localizedsections when the water content is permitted to drain away from one ofthe surfaces.

This freshly formed sheet 10 in plastic green condition is thenpreformed over a filter screen l2 forming a die as shown in Fig. 2, thesurface 13 of the screen 12 being accurately contoured to exactlyfit-the lower` cooperating surface of the upper die 15. The fibres 11 ofthe preformed sheet realine themselves in the new position of the sheeton the corrugated surface of the screen so that said fibres follow andare parallel to this surface at each point. The surfaces 13, 14 areaccurately shaped to press the preformed material between them tocompact it in variable manner producing higher concentration and greaterdensityin the inclined portions 16 between the crests 17.

As the dies 1 2, 15 approach each other the upper die surface 14 firstcontacts with the intermediate inclined portions 16 of the sheet, and asthese are pressed the area of Contact extends in each direction, andfinally closes over at the apexes of the crests 1'7. The sheetoriginally being formed wide enough to follow the curving Serial No.521,773

contour of the dies without any substantial amount of stretching, thedimension of the sheet will be exactly equal` to thedimensions of thedie and virtually no expansion takes place inpressinf,T due to the easewith which the water passes out through the filter screen 12 and theheavier supporting corrugating filter screen 4 which is placed over thebottom die 5, which in turn is slotted as indicated at 8 for thedrainage away of water removed by the pressing action. For a corrugatedsheet 397/8" wide the original sheet will be manufactured about 47%wide, the final corrugations having a pitch of about 51/2.

Fig. 3 shows the final sectional .shape of the sheathing with theinnersurface or valley 20 and the outer surface 21 of eachcrest 17 formed onequal radii R1, R2 around centers 22, 23 spaced apart a distance d equalto the final maximum thickness of the crest portion 17. The radii R1, Rzare preferably less than one half the pitch of the corrugations, i. e.,less than one half the distance of one crest to the next crest on thesame side of the sheathing, and also lessI than the height h of thecrest'on one side above the adjacent valley on the same side.

The original thickness t of the sheet l0 is only slightly greater thanthe maximum crest thickness d of the final sheathing, for instance, theoriginal thicknessmay be approximately ,-56", and this at the crest iscompressed to sgg in the final product. The vertical distance s at rightangles to a plane tangent to the crests is constant at all points of thecorrugatedsheathing and is equal to the maximum thickness d. Between thecrests the thickness measured normalto the surface at each pointregularly decreases to substantially constant thickness between theplane surfaces of the straight connecting portion 16 Where the thicknessis reduced to approximately 13/64" with corresponding increase in thedensity' of the material. Each crest 17 has its minimum density at thecenter and increases gradually in density towards the connecting portion16.

The original sheet 10 (Fig. 1) is preferably formed of a composition ofasbestos fibre and 100 Portland cement, and may, for instance, consistlof 25% of asbestos fibre and 75% of Portland cement. A filler may beused if desired in addition to the asbestos fibre and cement. In theHatschek process-the sheet 10p/ill normally con- 105 tain an excess ofmoisture and will be sufficiently uncompacted to readily permit ofreduction to the final shape (Fig. 3) by pressure between the imperviousupper die surface 14 and the lter screen *12, and similarly any othermethod of forming the sheet 10 should supply the sheet in suicientlyplastic and uncompacted form to permit the sheet to be readily preformedover the filter screen 12 without substantial disturbance of thecontinui' y of the composition and then to insure accurate nal shapingof the sheet between lter screen 12 and the die surface 14.

The product of this invention is very deeply corrugated in proportion tothe thickness of the material in its inally compressed form (Fig. 3).For instance, for an overall height or depth for' corrugation of 2" ormore, the maximum thickness of the material may be about g2g" or 15g, sothat the depth of corrugation will be four to eight times the maximumthickness of the material, and even greater proportionate depth ofcorrugation is permissible. The forming and pressing by the process ofthis invention leaves no weakness at the ridges or crests and thepreforming of the sheet permits the composition to be very accuratelycontrolled as to every part of the sheet, and with the bres alinedparallel to the surface at each point and following the curva ture ofthe sheathing in its final form.

The accurate tting of the upper and lower die surfaces produces-accuratefitting surfaces on the sheathing so that the sheathing strips willclosely contact at the area of overlap to forni a weatherproof joint.The formation of the sheathing wi h the curved crest portions and theintermediate straight connecting .porl'ions permits the dies to firstgrip the intermediate portions and hold them against shifting during thepressing of the remainder. At the same time the separation of the crestby the intermediate portion avoids extreme steepness of transition fromcrest to crest which would tend to cause sliding and cleavage of theplastic material under the action of the die pressing. This moderateinclination of the connecting portions 16 also avoids any extremethinning of the material at its intermediate portions and permits thefull quota of material to be included by compression and compacting.Consequently, substantially the same amount of material is included ateach portion of the sheathn ing and the thinness of the intermediateportions is oiset by increased compactness and strength.

In the sheathing of this invention there is sub stantially the sameamount of material in each transverse unit. It is compressed todifferent detained relative to the sheathing surfaces at each point, andwithout any irregularities developing weakness at any point.

I claim:

1. A sheathing of rigid asbestos cement composition comprising acorrugated sheet having curved crest portions of variable densityincreasving in each direction from the center of the crest,

and intermediate portions connecting said crests and of greater averagedensity than the average density of said crests.

2. A sheathing of rigid asbestos cement composition comprising acorrugated sheet having curved crest portions and intermediaterelatively thinner inclined portions connecting said crests, the depthof corrugation from the top of one crest and the lowest point of thenext succeeding valley between the crests being at least four times themaximum thickness of the sheathing material measured normal to thesurface at any point and opposite faces of said sheathing beingsubstantially identical in contour.

3. A sheathing of rigid asbestos cement composition comprising acorrugated sheet having curved crest portions of variable densityincreasing in each direction from the center of the crest, andintermediate portions connecting said crests and of greater averagedensity than the average density of said crests, the height ofcorrugation from the top of one crest to the lowermost point of the nextsucceeding valley being at least four times the maximum thickness of thesheathing at any point measured normal to the surfaces at that point.

4. A sheathing of rigid asbestos cement composition comprising acorrugated sheet having curved crest portions, and intermediate portionsconnecting said crests, each transverse unit of each of said portionscontaining substantially the same amount of material but varying indensity from one portion to another, the opposite faces of saidsheathing being substantially identical in contour.

5. The method of forming asbestos cement sheathing comprising mixingasbestos bres and cement with water and working the mixture intosubstantially flat sheet form with the fibres extending parallel to theplane of the sheet, immediately preforming said sheet while plastic overa corrugated lter screen and with fibres extending parallel to thesurface of the screen at each point thereof, pressing said sheet betweendies permitting the excess liquid to drain away and acting to compactthe material to greater density between the bends vof the corrugations,and then allowing said pressed sheet to set permanently in corrugatedform and with the opposite faces substantially identical in contour.

JOHN W. LEDEBOER.

